Ascorbate and glutathione regulation in hibernating ground squirrels.

Area of Science:

• Neuroscience
• Physiology
• Biochemistry

Background:

• Ground squirrels tolerate extreme reductions in cerebral blood flow during hibernation and arousal.
• Metabolic suppression is a key adaptation, but other neuroprotective mechanisms may also be involved.
• Understanding antioxidant dynamics is crucial for explaining tolerance to cerebral blood flow fluctuations.

Purpose of the Study:

• To investigate the changes in low molecular weight antioxidants, specifically ascorbate and glutathione (GSH), during hibernation in ground squirrels.
• To explore the potential neuroprotective role of these antioxidants during hibernation and arousal.

Main Methods:

• Collected plasma, cerebrospinal fluid (CSF), and brain samples (frontal cortex, hippocampus, cerebellum) from arctic ground squirrels (AGS) and 13-lined ground squirrels (TLS) during hibernation and non-hibernation periods.
• Utilized high-performance liquid chromatography (HPLC) to quantify ascorbate and GSH concentrations.
• Compared antioxidant levels between hibernating and non-hibernating squirrels, and during torpor versus arousal.

Main Results:

• Plasma ascorbate concentrations increased significantly (3-4 fold) in both species during hibernation and returned to baseline upon arousal.
• Cerebrospinal fluid (CSF) ascorbate levels doubled in hibernating AGS.
• Brain ascorbate content showed a slight decrease (10-15%) in both species, while plasma GSH levels remained stable or decreased slightly during hibernation.

Conclusions:

• Elevated plasma and CSF ascorbate concentrations during hibernation suggest a critical role in protecting the brain against oxidative stress.
• Ascorbate may be vital for neuroprotection during the challenging periods of torpor and reperfusion associated with arousal.
• These findings highlight a potential multi-faceted neuroprotective strategy employed by hibernating mammals.